The present invention relates generally to the fields of biology and agriculture 10 and more particularly to compositions and methods for use in fumigation of soils and structures.
The control of insects, plant pathogens, nematodes and weeds is of central importance to the agriculture industry. In particular, the substantial reduction or elimination of nematode populations in soils is critical to initial plant growth, productivity and life-span. Pathogenic fungi and nematodes develop on the extensive root systems of both annual and perennial crops, severely damaging them. Moreover, they persist in the soil after crop removal and need to be eliminated before replanting of new crops.
Soil fumigation is an essential practice for controlling nematodes and other soil-borne pathogens in many horticultural operations throughout the world. The need for this practice has been increasing due to the production of high-value crops where pathogen susceptible plants are grown in the same field without the benefit of appropriate crop rotations. Fields of this type of production are frequently covered by expensive structures to protect the crops from adverse conditions such as pests and inclement weather. Methyl bromide [MBr], a halogenated hydrocarbon, is the preferred chemical used throughout the world to fumigate soils. This broad-spectrum fumigant is used routinely in a variety of soils and climatic zones because its application requires minimal technology and virtually no knowledge of what pests are present in the soil. It is used extensively for soil fumigation as a commodity quarantine treatment (export and imports) to control a variety of pests on numerous crops and as a structural fumigant for wood destroying pests.
Unfortunately, methyl bromide is an xe2x80x9cOzone-Depleting Substancexe2x80x9d, i.e., a chemical directly involved in the destruction of the planet""s stratospheric ozone layer. Methyl bromide (MBr) is categorized as an ozone-depleting chemical with an ozone-depleting potential (ODP) of greater than 0.2 compared to trichlorofluoromethane (cfc 11), a refrigerant used as a reference gas having an ODP of 1. Evidence on the loss of MBr to the atmosphere after soil fumigation indicates that of the total amount applied to the soil for fumigation, approximately 87% is lost to the atmosphere within seven days. On reaching the stratosphere, MBr undergoes photo-oxidation, releasing bromine atoms which enter the ozone depletion cycle. Thus, its use in agriculture has been scheduled for phase-out. In the United States, methyl bromide will be banned as a soil fumigant in 2005. There is then a need to find alternative chemicals or methods to replace methyl bromide as a soil disinfectant.
Alternative approaches to fumigation include crop rotation, fallowing for at least four years, and use of pathogen and nematode-resistant crops. Unfortunately, resistance to plant pathogens and nematodes is available only in a few crops, and resistant cultivars may not be developed in the foreseeable future for many crops of significant commercial interest. Thus, soil fumigation remains the best alternative for control of plant pathogens and nematodes.
Currently available alternatives to MBr are less effective and more expensive. One proposed substitution for MBr is methyl iodide. Methyl iodide does not have the same deleterious effect on the ozone as MBr, and it acts in a similar fashion as MBr. Unfortunately, methyl iodide requires the same large dosages as MBr and can be relatively ineffective against nematodes. As illustrated in FIG. 1, methyl iodide was tested in a covered and uncovered state in a soil in various quantities up to 12 mg per kg of soil. The graph clearly shows that methyl iodide in such quantities is ineffective against nematodes in either a covered or uncovered environment.
Thus, the loss of MBr would be extremely costly to both agricultural producers and consumers as well as having a substantial impact on the U.S. economy. Nonetheless, it is the general consensus of those working in the field that no approach is currently available that will achieve the same level of broad-spectrum pest management as MBr. Chemical and non-chemical approaches that are available can provide some level of agricultural pest management, but it is generally with narrower activity and lower crop yields and quality. Therefore, there is clearly a need for alternatives to MBr.
The present invention provides both a method and composition for controlling deleterious organisms, such as insects, nematodes and weeds without causing significant harm to the ozone layer. Such deleterious organisms can be controlled by applying a compound comprised of both monoiodinated hydrocarbons and diiodinated hydrocarbons. Because of the chemical properties of the iodinated hydrocarbons, most notably their solubility, the mono- and diiodinated hydrocarbons can be combined to make an effective insecticidal and nematicidal formulation that gives a similar performance to that of methyl bromide against both insects and nematodes. Additionally, the combination can be an effective herbicide.
Additionally, a method of soil fumigation is provided comprising applying to a soil an effective amount of a fumigant selected from diiodinated hydrocarbons, polyiodinated hydrocarbons and combinations of both.
In one embodiment, the pesticidal composition for controlling deleterious organisms can also contain a compound consisting of mono-iodinated hydrocarbons and di-iodinated hydrocarbons.
Furthermore, a pesticide for controlling deleterious organisms is provided containing a compound selected from the group which consists of diiodinated hydrocarbons, polyiodinated hydrocarbons and combinations thereof